The Effects of Vancomycin on the Viability and Osteogenic Potential of Bone-derived Mesenchymal Stem Cells

Periprosthetic joint infections (PJI), caused by methicillin-resistant Staphylococcus aureus (MRSA), is the major cause of total hip arthroplasty (THA) failures. Traditionally, MRSA is treated with vancomycin, administrated intravenously or applied directly onto infected tissue. The effect of direct (as opposed to systemic) vancomycin treatment on bone formation and remodelling is largely unknown. The minimal inhibitory concentration (MIC) of vancomycin was determined by adding 200 μl of different concentrations (1 – 20 μg/ml) to actively growing cultures of S. aureus Xen 31 (methicillin-resistant) and S. aureus Xen 36 (methicillin-sensitive), respectively, and recording changes in optical density over 24 h. Bone marrow-derived and proximal femur-derived mesenchymal stem cells (bmMSCs and pfMSCs) from rat femora were exposed to 1 x MIC (5 μg/ml) and 4 x MIC (20 μg/ml) of vancomycin for 7 days. Cell viability was determined by staining with crystal violet and MTT (3-(4,5- dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide), respectively, and osteogenic differentiation by staining with Alizarin Red S. Vancomycin had no effect on the viability of bmMSCs and pfMSCs, even at high levels (20 μg/ml). The osteogenic differentiation of pfMSCs was partially inhibited, while osteogenesis in bmMSCs was not severely affected. The direct application of vancomycin to infected bone tissue, even at excessive levels, may preserve the viability of resident MSC populations. Short-term demineralization may thus be reversed after cessation of vancomycin treatment, improving the outcome of THA surgery.